The overall objective of this project is to determine how gonadotropin secretion is controlled in the male. Two general areas will be explored: control of FSH secretion in men, and control of GnRH secretion. Control of FSH secretion. Three aspects of this area will be studied. 1) FSH in urine will be measured by immunoassay in order to distinguish subnormal from normal FSH secretion and thereby define the role of FSH, compared to that of LH, in spermatogenesis. 2) Whether testosterone inhibits FSH secretion by inhibiting secretion of the preformed hormone or by inhibiting synthesis of the FSHBeta or Alpha subunit will be examined by treating men who have primary hypogonadism with testosterone enanthate and determining whether the intact FSH or one of the subunits decreases more rapidly. 3) The abnormality of control of FSH secretion that occurs in men with FSH-secreting adenomas will be explored by studying the characteristics of FSH release by cultured dispersed adenoma cells and by determining the characteristics of the FSH molecule by polyacrylamide gel electroptoresis. GnRH Secretion. GnRH in the peripheral plasma of men will be measured by immunoassay after it has been extracted in methanol and concentrated sixteen-fold. Plasma GnRH concentrations will be determined and compared to LH pulses in normal men, in men with idiopathic hypogonadotropic hypogonadism and men with primary hypogonadism, and in normal men given naloxone and dopamine.